The cylinders in an internal combustion engine can be disabled in order to reduce fuel consumption. This may be accomplished by cutting off the supply of fuel to selected cylinders, particularly to save fuel under light engine load conditions. This increases the load on the other cylinders and provides some pumping loss reduction, but still requires pumping work to move the air flow through all the cylinders.
Another method of cylinder disablement includes disabling or maintaining the intake and exhaust valves of the cylinder in a closed condition in addition to providing fuel cutoff to the deactivated cylinders. This method further reduces pumping work over simply providing a fuel cutoff to the deactivated cylinders, further increasing fuel efficiency. However, in order to cut off air flow to the deactivated cylinders, appropriate valve actuation hardware is required to keep the intake and/or exhaust valves closed during the deactivation mode of operation. The required hardware can be costly and results in additional hardware and software controls. As a result, cylinder deactivation systems may not be cost effective, or at least its cost effectiveness is reduced, due to these requirements. Therefore, further improvements in cylinder deactivation systems and controls are desired.